What is Addison’s disease?
Also known as hypoadrenocorticism, Addison’s disease is a potentially life-threatening deficiency in hormones produced by the adrenal glands.
These glands, located near the kidney, produce hormones such as cortisol, a stress hormone, and aldosterone, which regulates salt, sugar and water balance in the body.
Dogs with insufficient levels of these hormones can become very unwell. Addison’s disease is more common in young to middle-aged dogs, particularly females.
What are the symptoms of Addison's in dogs?
Signs of Addison’s in dogs typically include lethargy, lack of appetite, depression, reluctance to exercise, vomiting and diarrhoea. These may appear very suddenly and can be both intermittent and severe. Dogs suffering from the illness may also drink more and urinate more. It has been known for dogs with Addison’s to arrive at the vets extremely ill, in shock or collapsed, and almost in a coma. This is called an Addisonian crisis.
What causes Addison's in dogs?
Addison’s disease is usually caused by immune-mediated destruction of the adrenal glands. This means the dog’s immune system has become compromised and the adrenal glands have been damaged or attacked and therefore cannot produce enough hormones. Other less common causes include cancer and infections.
There are two types of Addison’s. The most common, or typical, form is due to lack of both glucocorticoids and mineralocorticoids and can be fatal. The less common, or atypical, form of Addison’s is due to a lack of glucocorticoids alone.
How is Addison's disease in dogs diagnosed?
Dogs with suspected Addison’s often collapse due to dehydration, low sodium, high potassium, low blood sugar and high calcium. Diagnostic tests on kidneys may also show up
In general, these clinical signs are enough for the vet to start treatment until a final diagnosis is established.
A final diagnosis is made if and when the vet establishes either very low levels of cortisol in the blood or by performing an ACTH stimulation test with a documented ‘little to no increase’ in the production of cortisol.
Is stress a factor in Addison's disease?
One of the reasons adrenal glands produce cortisol is to help dogs deal with stress and illness. If a dog cannot make enough of this hormone they may not be able to deal with stress or their symptoms will worsen when they are stressed. Stress is generally caused by a change in the dog’s routine. It’s important to minimise stress from your dog’s life.
Dogs who are very sick with Addison’s disease will often require hospitalisation and intravenous fluids.
What is the treatment for Addison's?
Dogs who are very sick with Addison’s will usually require IV fluids and close monitoring in hospital of their electrolytes (sodium and potassium). High levels of potassium can cause heart arrhythmias and lead to death. Once your pet has been stabilised in hospital and a diagnosis has been established, they will likely be started on their long term medication before going home.
Medication for Addison’s disease is needed for life and patients typically to do very well on it. Cases of typical Addison’s are treated with a combination of corticosteroids
(prednisolone) and mineralocorticoids (Zycortal). Zycortal is given by injection every 25 days. Dogs who only lack the corticosteroids (atypical cases), are only given prednisolone and monitored, although over time they might end up needing additional medication. Initially, when treatment is first started, your vet will need to recheck your pet’s electrolytes regularly to ensure the medication is working. This close monitoring will be reduced over time.
What is the prognosis?
As long as dogs receive the appropriate treatment, they can live a long and happy life. It’s worth noting, however, that anything that prevents the dog from getting their medication is likely to result in an emergency. Dogs with Addison’s have a lower immune system so even minor illnesses can be life-threatening and may not respond to treatment. The stress brought on by such an illness can lead rapidly to an Addisonian crisis.